数学高考难题请教老师们1

2025-12-18 00:41:17
推荐回答(1个)
回答1:

解:有题意可知,AB的中点在直线y=x+m上,且直线AB的斜率为-1,则
y1=x1^2
y2=x2^2
x1*x2=-1
(y1+y2)/2=(x1+x2)/2+m
(y1-y2)/(x1-x2)=-1
所以(y1-y2)/(x1-x2)=(x1^2-x2^2)/(x1-x2)=(x1+x2)=-1
(y1+y2)/2=(x1+x2)/2+m,即
x1^2+x2^2=x1+x2+2m
(x1+x2)^2-2x1x2=x1+x2+2m
即1-2*(-1/2)=-1+2m
所以m=3/2